1. Field of the Invention
The present invention relates generally to flexible solutions for protecting and sealing cable access locations, cable assemblies and optical interconnection points, and more specifically, it relates to flexible optical closures and optical connection terminals, and the performance and material properties of such closures and terminals.
2. Technical Background
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations, also referred to herein as “network distribution points” or “termination points,” at which one or more optical fibers are terminated from a distribution cable and spliced to other optical fibers of tether cables or fiber optic drop cables. These mid-span access locations provide a distribution point from the distribution cable leading to another distribution point, or a drop point from the distribution cable leading to an end user, commonly referred to as a subscriber, thereby extending an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” Based on the large number of mid-span access locations and the unique demands of terminated optical fibers at these mid-span access locations, protective enclosures are needed for maintaining and protecting the optical fibers, splice points and accessed portions of fiber optic cables at these numerous mid-span access locations positioned along the length of the distribution cable. Protective enclosures are also needed to maintain and protect, and in some embodiments seal, optical connectors and optical fibers of optical connection terminals spliced or otherwise interconnected with the mid-span access locations and positioned within the FTTx network.
Creating mid-span access locations and splicing tether or drop cables to them in the factory prior to distribution cable installation has been developed in order to eliminate the substantial expertise and experience required to access a distribution cable and configure optical connections in the field. In particular, it is not only difficult to access a distribution cable at a predetermined position once the cable is installed, but it is also difficult to access and identify a particular optical fiber of the distribution cable to be optically connected with an optical fiber of the tether or drop cable. Once identified, the optical fiber of the distribution cable is typically joined directly to the optical fiber of the tether or drop cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fiber of the distribution cable and the optical fiber of the drop cable are first spliced to a short length of optical fiber having an optical connector mounted on the other end, which is generally referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of an alignment member to properly interconnect the tether or drop cable with the distribution cable. In either case, the process of creating the mid-span access location and splicing the pre-selected optical fibers is not only time consuming, but must be accomplished by a highly-skilled field technician at significant cost and under field working conditions that are less than ideal.
Accordingly, the processes of creating access locations, terminating optical fibers and splicing the optical fibers to tether or drop cables was moved from the field to the factory with the introduction of pre-engineered solutions in which distribution cable assemblies including mid-span access locations are built in the factory for successful deployment and field installation. In addition to the problem of manufacturing these pre-engineered cable assemblies with their mid-span access locations in the proper positions, there are also problems encountered with using conventional components to protect the access locations and optically connect the optical fibers of the distribution cable with optical fibers of tether or drop cables at the mid-span access locations. For example, rigid enclosures are typically used to protect the section of the distribution cable that must be exposed to access the appropriate optical fibers and the splices. Distribution cables provided with conventional enclosures tend to be large in size and inflexible, and thus, unable to satisfy common deployment constraints, such as being wound onto a reel, deployed through conduits having a relatively small inner diameter or significant bends, or deployed through conventional aerial lashing equipment, such as sheaves and rollers. Furthermore, such enclosures are often structurally complex and difficult to install.
Thus, along with the development of pre-engineered cable assemblies, a need has arisen for a solution to replace the use of conventional rigid enclosures that are incapable of being installed within a factory and then deployed using typical cable installation methods (e.g., drive-off) without incurring any damage to the enclosure or optical fibers within. An enclosure solution for a pre-engineered cable assembly should not only meet or exceed the protection and sealing performance characteristics of conventional rigid enclosures, but should also allow the distribution cable to be installed using typical cable installation methods without damage to the enclosure, without compromising the sealing integrity of the enclosure and without exposing the optical fibers or splices to physical damage or significant attenuation caused by installation stress as defined by industry standards. In addition, it would be desirable to use those same material and physical properties of a flexible optical splice enclosure and apply them to other components of the pre-engineered cable assembly to aid in installation, such as optical connection terminals interconnected with the distribution cable at an access location and added in the factory. The flexible enclosures and other components would provide the pre-engineered cable assembly with a small enough diameter and the flexibility to be wound onto a reel, deployed through a conduit having a relatively small inner diameter or significant bends, or deployed using conventional aerial lashing equipment.